1. Field of the Invention
The present invention relates to cooling systems for a V-type engine including a V-type diesel engine.
2. Description of the Related Art
Generally, a water cooling system used in a V-type engine has the following structure and function (e.g., Japanese Patent Application, Laid Open Publication Nos. 62-91615 and 7-189694). A water pump is attached to one end of an engine in a crankshaft direction, and cooling water discharged from the water pump is distributed to both banks of the engine such that it flows through the banks in the crankshaft direction. The cooling water is then collected into a collection pipe at the other end of the engine and introduced to a radiator. Subsequently, the cooling water is returned to the water pump from the radiator.
In the meantime, an oil cooler of water-cooled type is sometimes provided for cooling an oil. In such a case, if the cooling water which has cooled the engine is used as a cooling medium for cooling the oil, the oil may not be sufficiently cooled since the cooling water is already hot.
To overcome this problem, proposed are oil cooler arrangements as shown in FIGS. 4 and 5. In the drawings, reference symbols xe2x80x9caxe2x80x9d indicates a water pump, xe2x80x9cbxe2x80x9d and xe2x80x9ccxe2x80x9d indicate a cylinder block and cylinder head of each bank of the engine, xe2x80x9cdxe2x80x9d indicates a collection pipe, xe2x80x9cexe2x80x9d indicates: a radiator, and xe2x80x9cfxe2x80x9d indicates an oil cooler.
In FIG. 4, the cooling water is bifurcated immediately downstream of the water pump xe2x80x9caxe2x80x9d and one branch flow of cooling water passes the oil cooler xe2x80x9cfxe2x80x9d prior to entering the cylinder block xe2x80x9cbxe2x80x9d of one of the banks. In FIG. 5, the cooling water is drawn out from an upstream portion of the cylinder block xe2x80x9cbxe2x80x9d of one of the banks and introduced to the oil cooler xe2x80x9cfxe2x80x9d and collection pipe xe2x80x9cd.xe2x80x9d According to these arrangements, the cooling water before used for cooling the engine is employed as the oil cooling medium so that sufficient oil cooling can be expected.
In FIG. 4, however, the hot cooling water, which has passed the oil cooler, is introduced to one of the banks so that temperature difference arises between the banks. The arrangement of FIG. 5 also has a problem that an amount (or flow rate) of cooling water which flows through one of the banks having the oil cooler xe2x80x9cfxe2x80x9d is smaller than the other bank. As a result, temperature difference arises between the banks.
As described above, the conventional arrangements cannot realize both the good cooling balance between the two banks and the good oil cooling performance.
In a normal arrangement, the water pump is located at a front end of the engine and the collection pipe is located at the rear end of the engine.
However, additional devices such as a fuel injection system (in the case of diesel engine) and a turbocharger are often situated at or near the rear end of the engine. Thus, it is difficult to locate the collection pipe, which is a separate element, at the engine rear end. Further, the existence of the collection pipe requires a larger space at the engine rear end.
An object of the present invention is to realize both the good cooling balance between the two banks and the good oil cooling performance.
Another object of the present invention is to equalize the temperature and amount of cooling water introduced to the two banks so that there is no temperature difference between the banks.
Still another object of the present invention is to design a compact engine.
Yet another object of the present invention is to eliminate a separate pipe connecting the banks so that the number of parts required is reduced and a layout problem does not arise in the engine room.
Another object of the present invention is to improve rigidity and reduce vibration noise.
According to one aspect/embodiment of the present invention, there is provided a cooling system for a V-type engine characterized in that cooling water supplied from a water pump is distributed to two banks of the engine after the cooling water passes an oil cooler.
Since the cooling water is introduced to the oil cooler before it cools the engine, it can cool the oil sufficiently. Further, since the cooling water is introduced to the banks after passing the oil cooler, temperature and amount of the cooling water to be entered to the two banks are equal. Thus, there is no temperature difference between the banks.
Preferably, the water pump is provided at an end of the engine in a crankshaft direction and a connection pipe connecting water jackets of the banks is provided at the other end of the engine such that the cooling water discharged from the water pump is caused to flow in the connection pipe after the oil cooler and is introduced to the water jackets of the banks from the connection pipe.
Preferably, the connection pipe has an inlet for accepting the cooling water from the oil cooler, at least two outlets positioned in series in a flow direction of the cooling water from the inlet and communicated with water jackets of the. banks of the engine respectively, and a throttle portion between the outlets for reducing a cross section of the connection tube.
The connection tube is preferably tapered between the outlets such that the connection tube is more throttled as it goes upstream, a most throttled portion preferably defines the throttle portion, and the throttle portion is preferably located immediately downstream of the upstream outlet.
It is preferred that the connection tube is integrally formed on a flywheel housing.
According to another aspect/embodiment of the present invention, there is provided a cooling system for a V-type engine characterized in that a connection tube for connecting water jackets of two banks of an engine is integrally formed with a housing member mounted on an end of the engine in a crankshaft direction.
Since the housing member which is generally mounted on an end of the engine in the crankshaft direction is used to integrally form the connection tube, a separate, pipe is unnecessary and therefore easy layout and size reduction are realized.
Preferably, the housing member is a flywheel housing.